Cardiovascular responses in older adults with total knee arthroplasty at rest and with exercise on a positive pressure treadmill.

PURPOSE: We investigated cardiovascular responses at rest and during submaximal exercise on a lower body positive pressure treadmill in older adults with total knee arthroplasty (TKA). METHODS: Twenty-four adults (mean age 64.6 ± 7.9 SD) with unilateral TKA participated (median time since surgery 8.0 weeks). Heart rate and blood pressure responses were measured at rest standing on the positive pressure treadmill with 0, 10, 20, and 30 mmHg applied. Heart rate, blood pressure, oxygen consumption, minute ventilation, knee pain and perceived exertion were measured during submaximal exercise tests (0 and 40% body weight support) conducted 1 week apart. RESULTS: At rest there were no differences in blood pressure across different treadmill pressures, but heart rate was significantly lower when 30 mmHg was applied compared to ambient pressure conditions (P < 0.05). Participants averaged 5.1 exercise test stages with 0% body weight support (maximum speed 2.5 mph, 0% incline) and 6.4 stages with 40% body weight support (maximum speed 3.0 mph, 10% incline). During exercise, heart rate, systolic blood pressure, oxygen consumption, and minute ventilation were lower when 40% body weight support was provided for a given test stage (P < 0.01). Diastolic blood pressure, knee pain and perceived exertion did not differ with body weight support but increased with increasing exercise test stages (P < 0.05). CONCLUSIONS: Provision of body weight support allowed TKA patients to walk at faster speeds and/or to tolerate greater incline with relatively lower levels of heart rate, blood pressure, and oxygen consumption.

Assessing exercise limitation using cardiopulmonary exercise testing.

The cardiopulmonary exercise test (CPET) is an important physiological investigation that can aid clinicians in their evaluation of exercise intolerance and dyspnea. Maximal oxygen consumption ([Formula: see text]) is the gold-standard measure of aerobic fitness and is determined by the variables that define oxygen delivery in the Fick equation ([Formula: see text] = cardiac output × arterial-venous O(2) content difference). In healthy subjects, of the variables involved in oxygen delivery, it is the limitations of the cardiovascular system that are most responsible for limiting exercise, as ventilation and gas exchange are sufficient to maintain arterial O(2) content up to peak exercise. Patients with lung disease can develop a pulmonary limitation to exercise which can contribute to exercise intolerance and dyspnea. In these patients, ventilation may be insufficient for metabolic demand, as demonstrated by an inadequate breathing reserve, expiratory flow limitation, dynamic hyperinflation, and/or retention of arterial CO(2). Lung disease patients can also develop gas exchange impairments with exercise as demonstrated by an increased alveolar-to-arterial O(2) pressure difference. CPET testing data, when combined with other clinical/investigation studies, can provide the clinician with an objective method to evaluate cardiopulmonary physiology and determination of exercise intolerance.

Optimizing pulmonary rehabilitation in chronic obstructive pulmonary disease--practical issues: a Canadian Thoracic Society Clinical Practice Guideline.

Pulmonary rehabilitation (PR) participation is the standard of care for patients with chronic obstructive pulmonary disease (COPD) who remain symptomatic despite bronchodilator therapies. However, there are questions about specific aspects of PR programming including optimal site of rehabilitation delivery, components of rehabilitation programming, duration of rehabilitation, target populations and timing of rehabilitation. The present document was compiled to specifically address these important clinical issues, using an evidence-based, systematic review process led by a representative interprofessional panel of experts. The evidence reveals there are no differences in major patient-related outcomes of PR between nonhospital- (community or home sites) or hospital-based sites. There is strong support to recommend that COPD patients initiate PR within one month following an acute exacerbation due to benefits of improved dyspnea, exercise tolerance and health-related quality of life relative to usual care. Moreover, the benefits of PR are evident in both men and women, and in patients with moderate, severe and very severe COPD. The current review also suggests that longer PR programs, beyond six to eight weeks duration, be provided for COPD patients, and that while aerobic training is the foundation of PR, endurance and functional ability may be further improved with both aerobic and resistance training.

Effects of the self-contained breathing apparatus on left-ventricular function at rest and during graded exercise.

The purpose of this study was to examine the effects of the self-contained breathing apparatus (SCBA) on left-ventricular (LV) function at rest and during mild- to moderate-intensity exercise, using 2-dimensional echocardiography. Twenty-three healthy male volunteers exercised on a stair-climber at work rates equivalent to 50%, 60%, 70%, and 80% of peak oxygen consumption. Esophageal pressure LV diastolic and systolic cavity areas, and myocardial areas were acquired during the final minute of each stage of exercise. As expected, the esophageal pressure response during SCBA breathing revealed significantly lower (more negative) inspiratory pressures and higher (more positive) expiratory pressures and, consequently, higher pressure swings, than free breathing (FB). End-diastolic cavity area (EDCA) and end-systolic cavity area (ESCA) were lower with the SCBA than with FB. LV contractility was higher (p < 0.05) with the SCBA, which can partially be explained by decreases in end-systolic wall stress. Therefore, the SCBA was found to decrease LV preload during moderate-intensity exercise, but did not negatively affect stroke area because of a similar reduction in ESCA.

Impaired exercise ventilatory mechanics with the self-contained breathing apparatus are improved with heliox.

The effect of the self-contained breathing apparatus (SCBA) with compressed air (BA-A) on ventilatory mechanics, work of breathing (WOB), pulmonary function, and respiratory muscle fatigue, was compared with that of a low resistance breathing valve (LRV). Further, the effect of unloading the respiratory muscles with heliox with the SCBA (BA-H) was compared with BA-A and LRV. Twelve men completed three randomized exercise trials on separate days, each consisting of three 10 min bouts of stepping exercise (Bouts 1, 2, and 3) separated by a 5 min recovery. Subjects wore firefighter protective equipment including the SCBA. At rest, FEV(1) and peak expiratory flow rates were lower with BA-A than with LRV, but were higher with BA-H than either with BA-A or LRV. After Bout 3, expiratory reserve volume, expiratory resistive WOB, and inspiratory elastic WOB were increased in BA-A compared to LRV but these were lower with BA-H compared to BA-A. After Bout 3, maximal inspiratory and expiratory pressures were reduced with BA-A, but not with LRV or BA-H. In summary, we found that the SCBA reduced resting pulmonary function, and increased expiratory reserve volume, work of breathing, and respiratory muscle fatigue during stepping exercise, and these changes can be reduced with the use of heliox.

The effect of trunk stability training on vertical takeoff velocity.

STUDY DESIGN: Randomized controlled trial with repeated measures. OBJECTIVES: To determine the effect of trunk stability training on vertical takeoff velocity. BACKGROUND: Trunk stability training is commonly used in sports training programs; however, the effects of stability training on performance enhancement are not known. Trunk stability training may provide a more stable pelvis and spine from which the leg muscles can generate action, may better link the upper body to the lower body, or may enhance leg muscle activation, thus promoting optimal force production during sporting activities such as a vertical jump. METHODS AND MEASURES: Fifty-five athletes were randomly assigned to 1 of 4 training groups: trunk stability (TS), leg strength (LS), trunk stability and leg strength (TL), and control (CO). Subjects were tested 3 times: at pretraining, after 3 weeks of training, and after 9 weeks of training. A repeated-measures analysis of covariance (ANCOVA) was used to examine differences among groups for vertical takeoff velocity measured indirectly using a force plate. Pretraining takeoff velocity and body mass were used as covariates. RESULTS: After 3 and 9 weeks, the training groups were not different from each other. After 9 weeks of training, all 3 training groups had a greater takeoff velocity than the control group (P<.05). After 3 weeks of training only the TS group had a greater takeoff velocity than the control group (P<.05). Only the TL group increased significantly in vertical takeoff velocity between the third- and ninth-week testing periods (P<.05). CONCLUSIONS: Nine weeks of trunk stability training was similarly effective in enhancing vertical takeoff velocity as leg strength training or the combination of trunk stability and leg strength training.

The effects of helium-hyperoxia on 6-min walking distance in COPD: a randomized, controlled trial.

BACKGROUND: We hypothesized that breathing helium-hyperoxia (HeO2) would significantly improve 6-min walking test (6MWT) distance in COPD subjects. METHODS: This was a blinded, randomized crossover study. At visit 1, we assessed pulmonary function, exercise capacity, and 6MWT distance. Visits 2 and 3 consisted of four 6MWTs in which the following different inspired gases were used: room air (RA) by mask; 100% O2 by mask (mask O2); 100% O2 by nasal prongs (nasal O2); and 70% He/30% O2 by mask (HeO2). Walking distance, shortness of breath, leg fatigue, O2 saturation, and heart rate (HR) were assessed. RESULTS: Sixteen COPD subjects participated (mean FEV(1)/FVC ratio [+/- SD], 48 +/- 8%; mean FEV1, 55 +/- 13% predicted). Subjects walked farther when breathing HeO2 (564 m) compared to RA (497 m; p < 0.001), mask O2 (520 m; p < 0.001), or nasal O2 (528 m; p < 0.001). Despite the increased distance walked while breathing HeO2, there was no increase in shortness of breath or leg fatigue. There was desaturation when breathing RA (8%; p < 0.001) and nasal O2 (5%; p < 0.001), which was reduced when breathing HeO2 (3%; difference not significant) and mask O(2) (0%; difference not significant). There were no significant differences in HR in the four 6MWTs. CONCLUSIONS: The use of HeO2 increased 6MWT distance in COPD subjects more than either mask O2 or nasal O2 compared to RA. The increased walking distance was not associated with increased shortness of breath or leg fatigue. The results suggest that clinical benefit would be obtained by administering HeO2 during exercise, which may have significant clinical implications for the management of COPD patients.

Effects of changes in lung volume on oscillatory flow rate during high-frequency chest wall oscillation.

BACKGROUND: The effectiveness of high-frequency chest wall oscillation (HFCWO) in mucolysis and mucous clearance is thought to be dependant on oscillatory flow rate (Fosc). Therefore, increasing Fosc during HFCWO may have a clinical benefit. OBJECTIVES: To examine effects of continuous positive airway pressure (CPAP) on Fosc at two oscillation frequencies in healthy subjects and patients with airway obstruction. METHODS: Five healthy subjects and six patients with airway obstruction underwent 12 randomized trials of HFCWO (CPAP levels of 0 cm H2O, 2 cm H2O, 4 cm H2O, 6 cm H2O, 8 cm H2O and 10 cm H2O at frequencies of 10 Hz and 15 Hz) within a body plethysmograph, allowing measurements of changes in lung volume. Fosc was measured by reverse plethysmography using a 20 L isothermic chamber near the mouth. At the end of each randomized trial, an inspiratory capacity manoeuvre was used to determine end-expiratory lung volume (EELV). RESULTS: EELV increased significantly (P<0.05) with each level of CPAP regardless of oscillation frequency. Fosc also significantly increased with CPAP (P<0.05) and it was correlated with EELV (r=0.7935, P<0.05) in obstructed patients but not in healthy subjects (r=0.125, P=0.343). There were no significant differences in perceived comfort across the levels of CPAP. CONCLUSIONS: Significant increases in Fosc with CPAP-induced increases in lung volume were observed, suggesting that CPAP may be useful as a therapeutic adjunct in patients who have obstructive airway disease and who require HFCWO.

The impact of exercise training intensity on change in physiological function in patients with chronic obstructive pulmonary disease.

Pulmonary rehabilitation incorporating exercise training is an effective method of enhancing physiological function and quality of life for patients with chronic obstructive pulmonary disease (COPD). Despite the traditional belief that exercise is primarily limited by the inability to adequately increase ventilation to meet increased metabolic demands in these patients, significant deficiencies in muscle function, oxygen delivery and cardiac function are observed that contribute to exercise limitation. Because of this multifactorial exercise limitation, defining appropriate exercise training intensities is difficult. The lack of a pure cardiovascular limitation to exercise prohibits the use of training guidelines that are based on cardiovascular factors such as oxygen consumption or heart rate. Current recommendations for exercise training intensity for patients with COPD include exercising at a 'maximally tolerable level', at an intensity corresponding with 50% of peak oxygen consumption (V-O2peak), or at 60-80% of peak power output obtained on a symptom-limited exercise tolerance test. In general, it appears that higher intensity training elicits greater physiological change than lower intensity training; however, there is no consensus as to the exercise training intensity that elicits the greatest physiological benefit while remaining tolerable to patients. The 'optimal' intensity of training likely depends upon the individual goals of each patient. If the goal is to increase the ability to sustain tasks that are currently able to be performed, lower to moderate-intensity training is likely to be sufficient. If the goal of training, however, is to increase the ability to perform tasks that are above the current level of tolerance, higher intensity training is likely to elicit greater performance increases. In order to perform higher intensity exercise, an interval training model is likely required. High-intensity interval training involves significant anaerobic energy utilisation and, therefore, may better mimic the physiological requirements of activities of daily living. Also, high-intensity interval training is tolerable to patients and may, in fact, reduce the degree of dyspnoea and dynamic hyperinflation through a reduced ventilatory demand. Another factor that will determine the optimal intensity of training is the relative contribution of ventilatory limitation to exercise tolerance. If peak exercise tolerance is limited by a patient's ability to increase ventilation, it is possible that interval training at an intensity higher than peak will elicit greater muscular adaptation than an intensity at or below peak power on an incremental exercise test. More research is required to determine the optimal training intensity for pulmonary rehabilitation patients.

Work of breathing is increased during exercise with the self-contained breathing apparatus regulator.

The self-contained breathing apparatus (SCBA) increases the expiratory pressure required to maintain high rates of ventilation, suggesting that the expiratory work of breathing (WOB) is increased; however, this has never been reported. The objective of this study, therefore, was to determine if the WOB is increased with the SCBA regulator (BA condition) compared with a low-resistance breathing valve (RV condition) during exercise. Twelve healthy male subjects underwent two randomized exercise trials, consisting of cycling at 150, 180, 210, and 240 W. Inspired and expired tidal volumes were measured using a body plethysmograph, whereas esophageal pressures were measured with an esophageal balloon. Modified Campbell diagrams were created to calculate the resistive and elastic components of WOB during inspiration and expiration. There were no differences in WOB between BA and RV conditions at 150 W. End-inspiratory and -expiratory lung volumes were elevated (p < 0.05) in the BA condition at higher ventilation rates, which increased inspiratory elastic work and decreased expiratory elastic work at 180 and 210 W (p < 0.05). At 240 W (VE=112 +/- 17 L.min-1 in the BA condition), active expiratory resistive work increased by 59% +/- 51%, inspiratory elastic work increased by 26% +/- 24%, and total WOB increased by 13% +/- 12% in the BA condition (p < 0.05). The SCBA regulator causes an increase in the active expiratory resistive work to maintain high ventilatory rates and an increase inspiratory elastic work through an elevation in lung volumes.

Reductions in functional balance, coordination, and mobility measures among patients with stable chronic obstructive pulmonary disease.

PURPOSE: To compare measures of balance, coordination, and mobility between patients with chronic obstructive pulmonary disease (COPD) and healthy control subjects, and to determine whether differences in these measures are associated with measures of disease severity. METHODS: The subjects were divided into three groups: 15 patients with COPD who required the use of supplemental oxygen (WO), 15 patients with COPD who did not require the use of supplemental oxygen (NO), and 21 healthy control subjects (CO). The subjects performed spirometry and several measures of balance, coordination, and mobility including the Community Balance and Mobility Scale, the timed up and go test, the fast-gait speed test, posturography, and both a finger-to-nose test and a toe-tapping coordination test. Significance was set at an alpha less than 0.05. RESULTS: When control was used for age, significant differences were found between the WO group and the CO group for the finger-to-nose test, and for both the sway index and peak sway index for the eyes open, moving-platform test. Differences were found among all three groups for the Community Balance and Mobility Scale overall score. The scores for the WO group were significantly worse than for the NO group on the timed up and go and the fast-gait speed tests. Moderate correlation was found among all of the measures, demonstrating significant differences in forced-expiratory volume in 1 second (FEV1), peak expiratory flow, and forced-expiratory volume. When controls were used for both age and FEV1, between-group differences disappeared. CONCLUSIONS: Patients with COPD exhibit deficiencies in functional balance, coordination, and mobility tasks associated with disease severity or differences in activity levels, but not in the requirement for supplemental oxygen.